Hardness of water is due to the pair if ions:

Options

A. `Ca^(2+) and K^(+)`
B. `Mg^(2+) and K^(+)`
C. `Ca^(2+) and Mg^(2+)`
D. `Ba^(2+) and Zn^(2+)`

Explanation

(c ) `Ca^(2+) and Mg^(2+)` ions cause the hardness of water